Shachiku Kishi ga S-rank Boukensha ni Hirowarete Himo ni Naru Hanashi: Yashinaware Nagara Slow Life

Theo is a young man who has lived while being harrassed and treated just like a slave ever since he joined the kingdom's order of chivalry five years ago. But one day, an S-ranked adventurer by the name of Leigh Silverhorn, aka "The Silver Princess", saves Theo's life while he is carrying out his duties. Then, in an unexpected turn of events, he becomes her housekeeper and begins living in her home. Leigh has incredible power and talent, but next to no means of earning a living. Thus, despite being wrapped around her finger, Theo starts his new life in the kitchen!